1. Field of the Invention
This invention relates to an image processing method and system. This invention particularly relates to an image processing method and system, wherein shutting light processing is carried out under desired conditions in a second image processing apparatus by utilizing a digital image signal, representing an image before being subjected to the shutting light processing, and which is formed bya first image processing apparatus, and an unsharp image signal, which represents an unsharp mask image used for the shutting light processing.
2. Description of the Prior Art
Recently, research of digital photo printers has been carried out. With the digital photo printers, an image recorded on photographic film (such as negative film or reversal film) or which is recorded on printed matter is photoelectrically read out. The obtained image signal is then converted into a digital signal which is then subjected to various kinds of image processing to produce a processed image signal. Thereafter, recording light is modulated with the processed image signal, and a photosensitive material such as photographic paper is scanned with and exposed to the modulated recording light.
In this manner, a visible image is printed on the photosensitive material.
With the digital photo printers, layouts of printed images, such as combining a plurality of images, dividing an image, and editing characters and images, as well as various kinds of image processing, such as color/image density adjustment, conversion of magnification, and contour emphasis, may be freely carried out. Therefore, prints edited and processed freely in accordance with certain applications can be obtained. Also, where conventional surface exposure techniques are employed, the image density information recorded on film, or the like, cannot be reproduced perfectly due to limitations imposed upon the reproducible image density range of photosensitive materials. However, with digital photo printers, prints can be obtained such that the image density information can be reproduced approximately perfectly. Alternately, prints may be obtained with image processing, or the like, by perfectly utilizing the image density information recorded on film.
Basically, digital photo printers comprise of a read-out means for reading out an image recorded on an image storage sheet, such as film, and an image reproducing means. The image reproducing means carries out image processing on an image signal detected by the read-out means, and adjusts exposure conditions. Also, the image reproducing means carries out a scanning exposure operation on a photosensitive material under the adjusted exposure conditions, and carries out development processing on the exposed photosensitive material. Further, the image reproducing means can reproduce a visible image from the image signal obtained from the image processing, and can display the visible image on a monitor.
For example, in a read-out apparatus for reading out an image recorded on film using slit scanning, reading light having a slit-like shape extending in a one-dimensional direction irradiates to the film, and the film is moved in a direction approximately normal to the one-dimensional direction. (Alternatively, the reading light and a photoelectric converting device are moved in the direction, which is approximately normal to the one-dimensional direction.) In this manner, the film is scanned in a two-dimensional direction. An image of the light, which has passed through the film and carries the film image information, is then formed on a light receiving face of the photoelectric converting device, such as a CCD line sensor, and is photoelectrically converted into a light amount signal. This light amount signal is amplified and then converted into a digital signal by an analog-to-digital converter. Thereafter, the digital signal is subjected to various kinds of image processing, such as compensation for a fluctuation in the characteristics among the CCD elements of the CCD line sensor, image density conversion, and conversion of magnification, and is transferred to a reproducing means.
In the reproducing means, for example, a visible image is reproduced from the received image signal and displayed on a display device, such as a cathode ray tube (CRT) display device. When necessary, an operator, viewing the reproduced image will correct the gradation, color and image density of the reproduced image (i.e., sets the set-up conditions). Where the reproduced image is judged as being an acceptable finished print, the image signal is transferred as the recording image information into a development means or a monitor.
In an image reproducing apparatus, in which the image reproduction with raster scanning (i.e., light beam scanning) is utilized, three kinds of light beams corresponding to exposure of the layers (which are formed on a photosensitive material and are sensitive to three primary colors, e.g. red (R), green (G), and blue (B)) are modulated in accordance with the recording image information, and then deflected in a main scanning direction (which corresponds to the aforesaid one-dimensional direction). Also, the photosensitive material is conveyed in a sub-scanning direction, which is approximately normal to the main scanning direction. (i.e. the photosensitive material is moved with respect to the deflected light beams and in the sub-scanning direction). In this manner, the photosensitive material is scanned in two-dimension with the light beams. Since these light beams have been modulated in accordance with the recording image information, and the image read out from the film is thereby reproduced on the photosensitive material.
The photosensitive material is then subjected to development processing, which is dependent on the particular kind of photosensitive material. For example, where the photosensitive material is a silver halide photographic material, it is subjected to the development processing comprising the steps of color development, bleach-fix, washing, drying, and the like. A finished print is thereby obtained.
Such a photosensitive material can record a comparatively wide range of luminance of the object. However, the maximum image density on the photosensitive material is limited. Therefore, in cases where a print of a scene having a large difference in luminance is obtained with an ordinary printing technique, details become imperceptible due to insufficient gradation in either one of a bright portion (a highlight) and a dark portion (a shadow) on the print. For example, in cases where a picture of a person is taken against the light, if the picture is printed such that the image of the person may become clear, the bright portion (such as the sky region) will become white and its details will become imperceptible. Also, if the picture is printed such that the bright portion, such as the sky region, may become clear, the image of the person will become black and its details will become imperceptible. In order to solve the problems, a shutting light technique or a masking print technique has heretofore been employed.
With the shutting light technique, an ordinary level of exposure is given to a region having an intermediate level of image density in a scene. Also, a long time of exposure is given selectively to a region, which has to become white such that the details of the region are imperceptible on the print, by using a perforated blocking sheet. Further, as for a region, which has to become black such that the details of the region are imperceptible on the print, the exposure time is kept selectively short by using a blocking sheet. In this manner, the print is obtained such that the contrast of each object may be kept appropriate, and the details of the highlight and the shadow may be kept perceptible. At least one such method has been proposed, in which unsharp image film photographically formed by the negative-positive reversal of the original image film is used as a blocking sheet for locally controlling the exposure time, and in which printing is carried out by superposing the original image film on the unsharp image film.
Also, various masking print techniques have been proposed in, for example, Japanese Unexamined Patent Publication Nos. 58(1983)-66929 and 64(1989)-35542 and Japanese Patent Publication No. 64(1989)-10819. With the proposed masking print techniques, the same effects as those of the shutting light technique may be obtained by locally changing the brightness of a light source for illuminating a photographic original image.
With the apparatus proposed in Japanese Unexamined Patent Publication No. 58(1983)-66929, a CRT is employed as the illuminating light source, and a photometric operation with memory scanning is carried out on an original image. In this manner, an unsharp mask signal is formed from the color original image. In an exposure mode, a CRT is controlled with the unsharp mask signal, and the contrast is thereby controlled such that the original image may be reliably recorded within the contrast reproduction limit of a photosensitive material.
With the apparatus proposed in Japanese Unexamined Patent Publication No. 64(1989)-35542, a CRT is employed as the illuminating light source, and an optical path for the photometric operation carried out on an original image and an optical path for the exposure of a photosensitive material are provided such that they may be changed over to each other. Also, a signal for controlling the luminance of the CRT during the exposure and thereby correcting the gradation and the saturation of the reproduced image is formed in accordance with the photometric signal obtained from the original image. Further, a signal for displaying the reproduced image on a monitor is formed. The image displayed on the monitor is viewed, and the amount of light of the CRT is thereby controlled such that a desired image may be reproduced.
With the apparatus proposed in Japanese Patent Publication No. 64(1989)-10819, a matrix device, such as a liquid crystal, which is capable of locally changing the light transmittance, is located between a uniform surface light source and an original image. The transmittance of the liquid crystal is controlled in accordance with the photometric signal obtained from the original image, and the contrast of the reproduced image is thereby adjusted.
Further, for example, in Japanese Unexamined Patent Publication No. 6(1994)-242521, a method is proposed wherein, in order for the gray balance in image reproduction to be corrected, conversion is carried out such that the maximum image density value and the minimum image density value of each color on an original image may become equal to predetermined values on the reproduced image. With the proposed method, the control of the gradation can be carried out for each of the frames of film. Therefore, as for a scene having a large difference in luminance, the gradation of the entire area of the image can be rendered soft such that the range of luminance of the scene may fall within the dynamic range of the photosensitive material. In this manner, the problems can be prevented from occurring in that the details of the highlight and the shadow become imperceptible due to insufficient gradation.
With the aforesaid shutting light technique and the aforesaid masking print techniques, the blocking sheet must be used, thereby requiring a very high level of technical operation. Additionally, considerable labor and time are required to form the unsharp image film.
Also, with the aforesaid apparatuses described in Japanese Unexamined Patent Publication Nos. 58(1983)-66929 and 64(1989)-35542 and Japanese Patent Publication No. 64(1989)-10819, the contrast of a comparatively large structure can be reproduced by adjusting with the distribution of the luminance of the illuminating light source. However, local structures in the reproduced image correspond to the projected image of the original image film. Therefore, the aforesaid apparatuses have drawbacks in that the reproduction of colors of the local structures, including their edges, cannot be freely controlled. Specifically, the sharpness of the edges, and the gradation of over-exposure portion and under-exposure portions, or the like, in the original image cannot be controlled freely.
Further, with the aforesaid apparatuses described in Japanese Unexamined Patent Publication Nos. 58(1983)-66929 and 64(1989)-35542 and Japanese Patent Publication No. 64(1989)-10819, the processing for the photometric operation and the exposure is carried out sequentially. Therefore, the problems occur in that the processing capacity cannot be maintained. Also, problems occur in that the printed image is disturbed due to the change in the distance of movement of the original image between when the photometric operation is performed and when the exposure is carried out. Further, with the apparatus described in Japanese Patent Publication No. 64(1989)-10819 which uses the liquid crystal, since the transmittance of the liquid crystal is at most approximately 30%, exposure time cannot be minimized. Furthermore, since the tube surface of the CRT is covered with glass, the side inward from the glass becomes luminous. Therefore, even if the film is brought into close contact with the tube surface of the CRT, a substantial spacing will still occur between the luminous surface of the CRT and the film. Accordingly, as to the apparatus proposed in Japanese Unexamined Patent Publication No. 64(1989)-35542, which displays an image represented by a photometric signal, a blur occurs in the photometric and image forming system due to the spacing between the luminous surface of the CRT and the film surface during the photometric operation. Therefore a clear monitor image cannot be obtained.
With the method proposed in Japanese Unexamined Patent Publication No. 6(1994)-242521, even though these types of problems can be prevented because the details of the highlight and the shadow become imperceptible due to insufficient gradation, other problems occur, in that the contrast of each object is degradul and the printed image becomes monotonous.
Therefore, novel image reproducing methods have been proposed, wherein an unsharp image signal representing only the structures of low frequencies in a color image, is subtracted from a digital image signal representing the color image. A difference signal is then obtained, processing for changing the image density, saturation, and/or gradation is performed on the difference signal, and a visible image is reproduced by an image reproducing means from the image signal, from the processing of the difference signal. In this manner, even if the contrast of the entire area of the original image is strong, a reproduced image can be obtained such that the contrast of the entire area of the image may be weakened, while retaining the contrasts of fine structures in the highlight and the shadow in the image, and while preventing the details of the highlight and the shadow from becoming imperceptible in the reproduced image due to insufficient gradation. Such image reproducing methods are described in, for example, Japanese Unexamined Patent Publication No. 2(1990)-226375 and U.S. Ser. No. 08/672,939.
In the image reproducing methods descried above, a filtering process is carried out on the image signal by using a low-pass filter to obtain and an unsharp image signal. However, if the size of the low-pass filter is very small, the sharpness of the resulting processed image will be unnaturally emphasized, and effects similar to those obtained with the aforesaid shutting light technique cannot be obtained. Therefore, in the image reproducing methods described above, the filtering process is carried out by using a filter having a comparatively large size (for example, a size of approximately 100.times.100). However, in cases where the unsharp image signal is formed with the low-pass filter, it is necessary for the processing to be carried out not only along the horizontal direction of the image but also along the vertical direction of the image. Accordingly, for the formation of the unsharp image signal, a number of line memories, equal to the mask size minus 1 must be used (for example, in cases where the filter size is equal to 100.times.100, 99 line memories must be used). As a result, the size of the apparatus for performing the processing cannot be minimized.
Accordingly, in Japanese Patent Application No. 7(1995)-337509, the applicant proposed a novel image reproducing method, wherein a dynamic range compressing process is used to reduce the size of the apparatus, while ensuring that a printed image having good image quality is thereby obtained. The proposed image reproducing method comprises the steps of: (i) carrying out a filtering process on an image signal with an infinite impulse response filter (IIR filter) to form an unsharp image signal, (ii) carrying out a dynamic range compressing process on the image signal in accordance with the unsharp image signal to obtain a processed image signal, and (iii) reproducing a visible image from the processed image signal.
The shutting light processing, in which the unsharp image is utilized, may be carried out with a digital photo printer system. However, a digital photo printer is a large-scaled apparatus and cannot be freely operated by ordinary users. Therefore, in cases where the shutting light processing, is used in the digital photo printer system, the aforesaid processing, including the shutting light processing, is currently performed by standardized technique in a development laboratory, such as a large-scaled image processing station. However, fundamentally, image correction processing, such as the shutting light processing, must be carried out in accordance with the intentions of the user who took the photograph. If standard processing is carried out in the development laboratory regardless of the user's intention, the shutting light processing cannot be carried out so as to satisfy the user.
For example, persons other than the user, cannot determine exactly which portion (a pattern of a person on the foreground side, a pattern of a person on the background side, a pattern of a person in the sun, a pattern of a person in the shade, or the like) in the photographed scene the user desires to have the most legible gradation.
Therefore, it is desired that the user be able to freely perform the shutting light processing suitable for the intention, with which he took the photograph. However, a digital photo printer system capable of satisfying such a requirement has not heretofore been proposed.